Actually, the standard stereo Design of these speakers (tweeter on top w/one midrange) lends themselves to small rooms for effectiveness with home theater!(assuming proper set-up..and I'll bet you have an easier time with the 804's in a small room!) Larger rooms tend to allow too much interaction with reflected sound with these for effective HT monitors! (In this respect, Diappolito condigured speakers work much better in larger rooms, where you sit further away!). So, my FIRST HAND experience with these 804's in a small room (approx 12 X 13), is that they work fantastic when set up properly!!! Definitely get the matching center for these 804's (the woofers being closer to the floor tend to make it easier to get good sound in the midbass with the 804's than the 805's probably!?).
As for your concern about small drivers handling the bass, actually NO FULL RANGE OR OTHERWISE monitor can handle full range bass from DD/DTS soundtracks!!!! Only exception is powered speakers with large drivers! Just about all full range monitors (even larger drivered units) bottom out or sound like week mush when you hit em with Digital bass mixes!!!...they just can't handle it! YOu really need a powered sub to handle the bottom (or two), and let your speakers be configured for "small" on the processor! The only downside to this, is that the standard 80hz crossover on most receivers "small" setting is really to high! 50-60hz is much much better, presserving the integrity and speed and punch in that portion of the bass region!...then let the sub handle bellow that! You'll need a pre/pro or receiver with flexible bass management however. Acurus, Aragon, Lexicon, B&K, Anthem, Theta, etc., all make processors with this advanced bass management flexibility!
Anyway, you can run the B&W's full range for music, as music isn't anywhere near as demanding in the deep bass as movie mixes, which are about 5-10 X's more potent there!!!A good choice for a small potent sub are the little Velodyne's or Sunfires.